This application relates in general to bonding one structure to another and more particularly to systems and methods for seal formation between surfaces.
Suitable bonding of two flat surfaces using solder and/or another bonding materials can be difficult to achieve when a hermetic seal, as well as close spacing between the structures, is desired. Often, in order for a hermetic seal to form in such a closely-spaced environment, the two flat surfaces must be maintained in a parallel orientation during the bonding (i.e., seal formation) process. For larger parts, this parallel orientation becomes more critical since the spacing difference (from low to high) across the parts is greater for a given angular mismatch.
In addition, the aforementioned two flat surfaces may belong to two parts of a device. In some instances, in order for assembled parts of a device to function properly in their intended application, such parts must be situated parallel to each other across the layer of solder or other adhesive, bonding the parts together.
However, when using existing press-together systems, it is difficult to maintain such parallel orientation as compression force is applied to the two parts during the bonding process. For example, unless carefully designed and constructed, during press operations a platen press system can elastically deform in such a way as to cause misalignment of the initially parallel surfaces. This deformation can cause misalignment of the structures being bonded. Furthermore, the bonding of the two structures by the press system may involve heating, such as for curing epoxy or melting solder. Such heat may cause the press and holding fixtures to expand, often unevenly. The result is an uneven clamping force and partial separation along the bond, leading to poor adhesion and the lack of a hermetic seal.
In accordance with the present invention, systems and methods for hermetic seal formation between at least two members in a closely-spaced environment are taught. In accordance with the invention, parallel orientation of the two members to be bonded is achieved by an induced pressure-difference between the environment outside of the members being bonded and that of the environment within the assembly containing those members. The pressure differential induces evenly-distributed compression force, thereby facilitating substantially uniform, and thus parallel, spacing between the two members.
In accordance with the present invention, a seal formulation assembly process begins with an adhesive structure (such as, for example, solder, epoxy, or another sealant) being positioned between a first member and a second member. After the members are positioned with respect to each other, they are brought together mechanically. If necessary, heat can be applied at this time. A reduction of internal pressure relative to the outside or ambient pressure is then induced within the assembly creating the necessary pressure difference for joining the two members.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.